I would go crazy without Scrivener keeping track of all the elements in my books. I keep writing skill notes, screenwritingU class notes, and everything so I have it in one place. There is a bit of a learning curve, but it's fantastic and dependable software. It can make backups too.
I'm looking forward to the organizational capabilities the most, I think. I've been using Apple Notes, which is surprisingly flexible and lets you make and nest folders and all that, but it doesn't port directly to a finished project, and there's a ton of work to get things publish-ready.
Compiling into an ebook is straightforward once things are setup. Going from v1 to v3 was frustrating, but there's community support, and they have quick answers. Setting up styles and sticking to them is a good way to be consistent. I generate a doc and format it separately for paperback.